Frost Heave and Water Uptake Relations in Variably Saturated Aggregate Base Materials

Abstract

The occurrence of frost heave in soils and aggregates can be attributed to the redistribution of water in the soil profile. Frost heave testing performed in this study on 71 variably saturated specimens of aggregate base material indicates that although the uptake of new water from outside the soil body is a primary source of moisture in the formation of segregation ice, internal water residing within the soil or aggregate structure can serve as an important supply of water to the freezing front. Frost heave concepts relating to unsaturated soil conditions were reviewed, and a laboratory methodology was employed to study the relationships between the physical properties of the specimens and their frost heave behavior. Degrees of saturation ranging from 45% to 84% were evaluated, and heave–uptake ratios as high as 2.24 were calculated. Ratios less than 1.09 suggest that sufficient porosity exists in the sample matrix to allow the formation of ice without causing frost heave; higher ratios designate samples that are nearly saturated and that undergo substantial upward redistributions of existing water during the initial freezing process, which gives rise to measurable heave even before additional water is imbibed by the sample. The entry of air into freezing soils and aggregates can play an important role in their frost heave behavior.